35C3: Add some more signs as png files

content/events/35c3/signs/35c3sign-eow.png

content/events/35c3/signs/35c3sign-notices-ausgewaffelt.png

content/events/35c3/signs/35c3sign-notices-ccc-helpdesk.png

content/events/35c3/signs/35c3sign-notices-pfand-1-euro.png

.../events/35c3/signs/35c3sign-notices-waffelstillstande.png

content/events/35c3/signs/35c3sign-notices-woc-helpdesk.png

...vents/35c3/signs/35c3sign-sonstiges-noc-access_switch.png

content/events/35c3/signs/35c3sign-waffelschlange-120min.png